Asphalt exhaust gas processor
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I have been working on asphalt exhaust gas treatment units recently; as the manufacturer is installing several new units, the existing equipment has been modified, with its capacity being increased three times compared to the original version. The number of exhaust gas processors has been reduced from six to two; I believe the air flow rate will remain the same. In theory, there is no need to change the blowers and exhaust fans. After on-site measurements as shown in the attached photos, it was found that the temperature at the outlet section at the back of the exhaust gas processors was very high, to the point where the enclosures turned red hot. Given that the insulation materials inside are similar, the front part of the furnace consists of a 100 mm thick layer of 1260-grade refractory fiber asbestos blanket, along with a 25 mm thick layer of 1400-grade refractory fiber blanket, giving a total thickness of 125 mm. The rear part, on the other hand, has only a 100 mm thick layer of 1260-grade refractory fiber asbestos blanket. Is it because the exhaust fan doesn’t have enough power, causing some of the smoke to leak out and damage the casing? It’s still due to insufficient insulation of the refractory material. I tend to think it’s the first reason; upon closer inspection of the photos, it can be seen that the area around the plug valve opening and the cold air inlet are severely damaged, while the other side of the furnace (the back side of the plug valve) seems to be in better condition. Could someone with expertise in manufacturing give some advice?
The exhaust gas was not completely burned in the front section; secondary combustion occurred after air entered later. Heat recovery should be considered; releasing heat into the atmosphere is a waste.
You mean that the air supply in the earlier stage was insufficient, and the amount of air should be increased.
From a process perspective, the intended design should be to add air for mixing and cooling after combustion before discharge. Currently, it seems that the insufficient temperature in the earlier stage led to incomplete combustion, so combustion continues in the later stage. Is the furnace too small, resulting in insufficient residence time and combustion temperature?
This post was last edited by richardpai on 10/8/2018 at 10:45. Based on the available information, the analysis is as follows: Incomplete combustion within the furnace results in a certain amount of combustible substances remaining in the gas as it reaches the subsequent air supply ports. Additionally, the temperature of the gas is high, allowing for secondary combustion once it mixes with oxygen-rich air in the air supply section. Due to the large amount of heat released by combustion at the air supply opening, the temperature rises significantly, causing the outer tube to heat up and turn red.
Based on everyone’s responses, I’d like to clarify a few points: 1. Can I determine the composition of the exhaust gas before it enters the furnace, and then use that to calculate the required amount of air as well as the combustion temperature in the furnace? Based on the measured furnace temperature, decide whether to heat the air (should the exhaust gases from combustion be used to heat the combustion air?) ) 2. By collecting samples from the asphalt exhaust gas after combustion, the thermal load of the flue gas can be determined, which in turn allows for the determination of the furnace’s structure and diameter Flame length? Some colleagues said that the flame length inside the furnace is long, and the temperature of the outer flame is high; this outer flame is located right in the cooling section, which causes the cooling section to reach high temperatures and turn black. 3. Can the gas flow rate inside the furnace be estimated at 15 m/s? By using the maximum flow rate of the exhaust fan, I was able to estimate that the actual flow velocity in the furnace is 2 m/s. The parameters indicate that it takes approximately 1 second for the asphalt waste gas to burn; the actual length of the combustion section of the furnace is 2.5 meters. Based on this, it seems that the length of the furnace is sufficient, right? I’m back after the holiday; I’d appreciate everyone’s advice – should I proceed with an expansion and renovation based on the existing structure, or should I gather the receipts and have a professional do the calculations?
Pour some cold water on the original poster to calm down. For non-standard equipment like incinerators, it’s better to turn to professional manufacturers for handling them, including the analysis of exhaust gas components; it’s also advisable to consult a laboratory department or a professional third party for this purpose. If the original poster makes the changes themselves and something goes wrong, their career will be over. The original poster should think twice.
Regarding the blowers on site, the manager said they should be removed, and instead a exhaust fan should be used to introduce the air necessary for combustion as well as the air used for cooling? Is it possible? His idea is to ensure the safety of the system, preventing gas from flowing back into the reaction vessel (the source of waste gas) in the event of a failure in the exhaust fan.